C6 and C7 types were studied in 158 Japanese patients with different types of chronic glomerulonephritis: 75 patients with IgA nephropathy (IgA-N); 49 patients with idiopathic membranous nephropathy (IMN), and 34 patients with minimal-change nephrotic syndrome (MCNS). There were significant differences in the C6 and C7 allele and phenotype frequencies between the patient groups and controls. A strong association was found between IgA-N and C7 5 phenotype (p < 0.001, RR = 12.71), and between MCNS and C7 5 phenotype (p < 0.001, RR = 14.20). A significant association between MCNS and C6 B2 phenotype (p < 0.05, RR = 2.42) was also found. In the IMN patient group, a significant association with C7 4 phenotype (p < 0.05, RR = 2.42) was observed. Thus, C6 and C7 phenotypes may be causative factors in the development of chronic glomerulonephritis.